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Light on gas Reducing methane emissions from livestock may be a step closer, thanks to the discovery of a previously unknown bacteria from the gut of an Australian marsupial.

Herbivores, such as sheep, cattle and wallabies, produce methane while digesting plant material, and release the gas build-up by belching.

It has been known that Tammar wallabies (Macropus eugenii) produce only one-fifth of the amount of methane compared with ruminants like cows and sheep.

Researchers believe this is due to a number of factors including the shape of their gut, the speed at which food passes through it, and the microbes that help break the food down. But until recently, they have been unable to identify all the species responsible.

To identify the mystery bacteria in the wallaby's gut, Morrison and colleagues turned to the relatively new field of metagenomics.

Picking out the pieces

The researchers, whose study is published today in the journal Science, used DNA sequence data and an advanced computer program to isolate fragments of the bacteria's genome from a microbial community of around 500 different bacterial species.

Computer analysis was used to combine the pieces and interpret the biological roles they encode. From this, an appropriate medium was designed to culture the bacteria into a pure form.

"This bacterium, known as Wallaby Group-1 (WG-1) thrives in an oxygen-free environment, which is one of the keys to its success," says Morrison.

"When the diet is high in starches and soluble sugars it flourishes, outnumbering many other microbes and resulting in a different method of feed digestion." This results in less methane being produced.

"Additionally this strategy also results in more energy being made available for animal nutrition rather than losing some of the digestible energy as a waste gas."

Benefits for cattle producers

Morrison says the goal now is to work with other local and international groups to find ways to improve the efficiency of digestion and nutrient capture by the animal.

"We want a win-win situation: something that's not only considered good for the environment, but also enhances animal productivity and profitability," he says.

The researchers have also discovered that WG-1 has distant relatives living in ruminants' stomachs.

"We are planning to use our collective knowledge of wallaby microbiology and the same approaches now to recover the relevant species from livestock then experiment with ways of making them grow more abundantly," says Morrison.

"The seed is already present. We just need to nurture it and make it bloom."

Dr Tom Davison, manager of Climate Change Research and Development at Meat and Livestock Australia agrees.

"This is an important piece of basic research that will assist us in our understanding of how we might be able to manipulate distant relatives of this family of bacteria that also exist in ruminant livestock, such that we produce less methane from cattle and sheep in our current feeding systems."